May be both naturally occurring or synthetically made, and may be added to processed food to prevent spoilage and extend shelf-life. According to the Canadian Food Inspection Agency (CFIA), preservatives are grouped into different classes, with each one having similar microbiological or chemical activity.
Class I: Curing preservatives in meats and cheeses
Class II: Antimicrobials
Class III: Antifungals
Class IV: Antioxidants and antioxidant synergists
All preservatives found in products in Canada must be approved for use by Health Canada.